More of the same old unimaginative thinking, that she must have some connection to some Time Lord or other even though her particular kind of death and resurrection is clearly very different from what Time Lords do. She's River! She's Romana! She's an inexplicably incestuous Susan! She's the Master's niece! She's the Rani! She's the Meddling Monk! She's Chancellor Goth back for sexy revenge!
Can't anyone come up with a theory that isn't Gallifrey-related? Something actually creative for a change?
I agree with you're overall ideas here, that those types of ideas are unoriginal. However, I don't think we have enough data at this point to really have an idea of what she is.
Sure, we can come up with creative ideas but would just be wild speculation at this point. There's a million things she could be, but I wouldn't place money on any one of them at this point!
So, I'm just waiting for now. We're not meant to know at this point.